It is known to use polymer latexes as a constituent of coating compositions for coating surfaces to be printed on, e.g., in an offset printing process. One type of composition typically used for paper coating applications of this general kind is styrene/butadiene (SB) copolymer latexes prepared by polymerization of styrene and 1,3-butadiene. For improving printability, acrylates such as butyl acrylate are typically incorporated into the composition. In particular, compositions in paper coating applications are desired to provide good binding properties, such as wet and dry binding strength, as well piling resistance to hold multiple printing stations ink-paper surface splitting forces during commercial offset printing process, and a balanced application profile of paper gloss, ink gloss and ink set-off properties.
Polymer latexes are also used as a binder component in carpet backsizing composition. In this type of application, the backsizing needs to provide high tuft bind, high secondary backing adhesion, and retention of strength on exposure to moisture while being flexible for ease of carpet installation and carpet pattern matching.
Organic peroxides such as alkyl peroxides and redox pairs are known in the art to be used as polymerization initiators in polymer latex compositions (see, e.g., U.S. Pat. No. 5,837,762). Further, for controlling the molecular weight of the polymer molecules, it is known in the art to add so-called chain transfer agents, for instance sulfur-containing compounds such as mercaptans (cf. EP 2 085 409). Hydroperoxides are also described in the art as substitutes for mercaptan chain transfer agents for addressing odor issues (see, e.g., EP 1 380 597).
U.S. Pat. No. 2,569,506 describes the emulsion polymerization of vinyl compounds using in combination a mercaptan modifier, a hydroperoxide catalyst, and oxygen. The authors further use an “activating salt” as a redox system.